Rotary drill bit



Feb. 3, 1931. L. (1. BLACK 3 9 ROTARY DRILL BIT Fil d ar h 8. 1925 2 Sheets-Shet 1' m/vew foe.

Feb. 3, 1931. 1.. c. BLACK rifigipggfi ROTARY DRILL BIT Filed March 8, 1923 2 Shemisfiheat 2 mma.

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Patented Feb. 3, 1931 van-"en LESTER C. BLACK, OF LOS ANGELES, CALIFQRNIA ROTARY v DRILL BIT Application filed March 8, 1923. Serial No. 623,600.v

The invention relates to drill bits for use in drilling oil wells.

An object of the invention is to provide a drill bit ofsuch construction that it may be made of alloy steel which cannot be practically machined. I

Another object of the invention is to provide a self-sharpening or self-dressing rotary drill bit. The invention possesses other advantageous features, some of which with the fore going will be set forth at length in the following specification where I shall outline in full, that form of the invention which I have selected for illustration in the drawings accompanying and forming part of the present specification. In said drawings I, have shown one form of drill bit embodying my invention, but it is to be understood that I do not limit myself to such form, since the invention as set forth in the claims, may be embodiedin a plurality of forms.

Referring to said drawings: Figure l is a perspective view of the assembled rotary drilling tool of my invention. Figure 2 is a perspective view of the joint between the two parts of the tool, the parts being detached. 7

Figure 3 is a vertical section through the shank and the head of the drill bit. Figure 4' is a top or plan view of the drill bit.

Figure 5 is aside elevation of-the drill bit. Figure 6 is a three-quartcr elevation of F the drill bit.

Figure 7 is an end elevation of the drill bit. I 1

One of the objects of my invention is to provide a rotary drill bit of a very tough steel alloys have extreme wear resisting qualities, but their characteristics are such that they cannot be practically machined. It is therefore practically impossible to turn a thread on a steel alloy bit of this the. purpose of attaching it to the drill tube. In accordance. with my invention, therefore. I form the drilling tool in two parts, one of said parts being a bit of steel alloy and the other part being a shank of steel or wrought steel alloy such as manganese steel. These nature for iron that may be readily machined. I provide means for rigidly and securely attaching the shank to the bit so that an integral structure'is in'effect produced and provide the shank with means for attachment to the drill tube. i

In accordance witlrmy invention I pro vide the head 2, of the drill bit 3 with a transverse groove or socket 4, the side walls 5 of which are inclined downwardly and outwardly to form a socket 0r dovetail slot of increasing width towards its base. The shank 6 of the drill tool is provided on its lower end with a projection 7 of increasing width towards its lower face 8 and this projection is adapted to bemoved transversely and fit into the socket in the drill bit. The projection is of such size, relative tothe socket, that there is sufiicient clearance to permit the projection to be easily inserted in tends downwardly below the upper edge of the head of the bit, thus forming anabutment at each side of the socket to prevent transverse displacement of the'projection in the socket. A left hand thread for the oollaris provided so that any friction encountered while revolving thetool in a r ight hand direction in the well will tend to tighten the. joint. 'T he shank 6 is provided on its upper end with a threaded tool joint'pin 11 for connection vith the drilling tube. The shank is provided with a longitudinal passage 12 therethrough which extends to and opens .on the lower face of the projection 7, to'forin a passage for the drilling mud or water through the shank. The head 2 of the bit is similarly the socket. Means are provided for clainpprovided with a passage 13 which opens-onto the base oftlie soeket'and when the projec-' tion is properly positioned int-he socket,i'

the two passages 12 and 13 are in alinement. The drill bit is provided below the head with a hollow enlargement 14, through which the passage extends. he mud is conducted from the passage 12 in the shank to the desirable pointof discharge with respect to the cutting face of the drill bit, by means of a pipe 16 inserted through the passage 13 in the drill bit and screwed into the passage 12 in the shank.

T he drill bit is preferably made of a hard steel alloy, such as manganese steel, and comprises a twisted blade member such as cutting blade 21 having a helicoidal surface 22 forming a sharp angle with the formation to be cut so that the abrasion of the formation maintains the cutting edge. The blade has a surface generated by a narrow rectangle moving parallel to its surface and rotating about 1 its axis of symmetry. The lower edge of the blade is perpendicular to the axis of symmetry and the width of the blade is constant for substantially its whole length so that the side edges of the blade serve as a reamer to maintain the diameter of the hole. The inclination of the blade to the horizontal is such that as the blade is worn away by abrasive contact with the formation, its cutting edge is continually sharpened. The blade is interrupted along its axis of symmetry to provide a passage 23 to permit the pipe to be inserted in the drill bit and to provide a passage or course for the water or mud discharged from the pipe. The blade thus presents, at its cutting edge, two cutting edges diametrically opposed to each other with respcct to the axis of symmetry of the blade. The blade is preferably a warped surface formed by the uniform rotation about a stationary axis of an element maintained parallel to a surface and moving uniformly from the surface, the axis passing through the element. This produces ablade of constant inclination over its whole length, so that as the blade wears down, due to the abrasive action of the formation, the angle of inclination of the blade with respect to the formation remains constant. It is not essential, however, that this constant angle of inclination be maintained, but it is preferable. y forming the blade in this manner and by making it out of avery hard steel alloy, the blade continually redresses itself during its rotation against the formation and can be used continually until it is practically all worn away. This construction allows a maximum amount of metal to be worn away from the lower or cutting edge of the bit without necessitating removal of the bit from the well for the purpose of dressing.

I claim:

1. A, rotary drilling tool comprising a twisted blade member the lower edge of which is formed with cutting ed es, the central longitudinal portion of which is formed with a passage, and the upper end of which has an integrally formed dovetail slot extending transversely of the plane of the upper portion of the blade member, the bottom of said slot being below the upper end of the blade member, a shank having an end formed to fit in the dovetail slot, and provided with a water passage registering with the first-mentioned passage, and a collar on the shank adapted to engage the upper end of the blade member.

2. A rotary drilling tool comprising a twisted blade member the lower edge of which is formed with cutting edges, the upper end of the blade having an integrally formed dovetail slot extending transversely of the plane of the upper portion of the blade member, the bottom of said slot being below the upper end of the blade member, a shank having an end formed to fit in the dovetail slot, and a collar on the shank adapted to engage the upper end of the blade member.

In testimony whereof, I have hereunto set my hand.

LESTER C. BLACK. 

